A skeletal visitor of types with default behavior appropriate for
the RELEASE_6
source version.

WARNING: The TypeVisitor interface implemented
by this class may have methods added to it in the future to
accommodate new, currently unknown, language structures added to
future versions of the Java™ programming language.
Therefore, methods whose names begin with "visit" may be
added to this class in the future; to avoid incompatibilities,
classes which extend this class should not declare any instance
methods with names beginning with "visit".

When such a new visit method is added, the default
implementation in this class will be to call the visitUnknown method. A new abstract type visitor
class will also be introduced to correspond to the new language
level; this visitor will have different default behavior for the
visit method in question. When the new visitor is introduced, all
or portions of this visitor may be deprecated.

Note that adding a default implementation of a new visit method
in a visitor class will occur instead of adding a default
method directly in the visitor interface since a Java SE 8
language feature cannot be used to this version of the API since
this version is required to be runnable on Java SE 7
implementations. Future versions of the API that are only required
to run on Java SE 8 and later may take advantage of default methods
in this situation.